There has so far been known a belt type power transmission apparatus as a vehicular continuously variable transmission (hereinafter simply referred to as “CVT”). The belt type power transmission apparatus comprises a drive side pulley and a driven side pulley respectively serving as movable sheaves, and an endless power transmission belt wound around the drive side pulley and the driven side pulley. The power transmission belt to be used for such a CVT is constituted by an endless band-like ring serving as a core material, and a multiplicity of elements each having a predetermined thickness in the axial direction of the endless band-like ring and retained by the endless band-like ring. The elements are subject to being pressed toward the axial direction of the endless band-like ring and serve to impart tensions to the endless band-like ring to transmit torque from the drive side pulley to the driven side pulley.
As this type of the power transmission belt, there is known a power transmission belt which is formed in the outer circumferential portion of the power transmission belt with a concave portion for accommodating, for example, an endless band-like ring, and has contact surfaces to be in contact with the pulleys and formed at the both end portions of the elements. An engagement portion having two neighboring elements engaged in concave-convex engagement with each other in the thickness direction of the element is formed at the inner end portion side of the element occupying the inner circumferential side of the power transmission belt (see, for example, Patent Document 1). The power transmission belt is constructed to have the concave portion of the element enlarged toward the inner bottom side portion of the concave portion from the opening side portion of the concave portion, and to have a plurality of endless band-like rings each having a width smaller than that of the opening of the concave portion accommodated in the concave portion of the element in side-by-side relationship with each other, thereby facilitating the elements to be assembled with the endless band-like rings.
As another power transmission belt, there is known a power transmission belt which comprises a multiplicity of elements each having a pair of left and right concave portions opened at the both side ends of the elements in the width direction of the power transmission belt to receive therein two endless band-like rings respectively, thereby enabling the multiplicity of elements to be retained by the two endless band-like rings. The known power transmission belt is constructed to have an engagement portion having two neighboring elements engaged in concave-convex engagement to be formed at the outer end portion of the element positioned outwardly of the endless band-like rings. The known power transmission belt is formed with contact surfaces to be in contact with the pulleys at the both sides of the elements in the width direction of the power transmission belt and at the inner end portions of the elements positioned inwardly of the endless band-like rings (see, for example, Patent Document 2).
These power transmission belts are each formed with a rocking edge on one side of the element, and constructed to have the plurality of elements relatively rockable with respect to the neighboring elements while being in pressing contact with the driven pulley in the axial direction of the endless band-like rings in the state that the elements are in contact with the elements each led by the rocking edge in the section in which the power transmission belt is being wound around the driven pulley.